The present invention regards a system of components for the diffuision of sound, which is particularly suitable for permanent or semipermanent installations in venues dedicated to the production or reproduction of music, speech, sounds or vibrations, outdoors, in cinemas, auditoriums and in all indoor rooms in general.
New digital technology in the sound recording field has made it possible to record part of the sound spectrum with absolute fidelity, such as the low and especially infra-low frequencies, those below the levels which are audible by the human ear and are perceptible by the body as vibrations.
This technology is also characterized by the absence of distortion of the original wave shape at a much higher sound level than was and is possible with analog systems. Particularly, in analog systems adding to the pickup problems Insurmountable mechanical and electromagnetic limits which are found during the storage or recording phase of the program on magnetic tape or vinyl records, it is absolutely impossible to exceed a certain level of dynamics, especially in the frequency bands in question, and to contain the distortion and therefore the degradation of the original signal within negligible limits.
In short, present digital systems enable the recording and the reproduction of a much wider dynamic range than is usually audible or necessary for the sensitivity of the human ear, maintaining great fidelity with features of low distortion and useful passband.
However, although this possibility is now widely accepted during recording and future development is looking to record further infinitesimal qualitative details, the possibility of reproducing the dynamic range by means of a modem amplification system is not as widely achieved.
In fact, in spite of the extensive technical/scientific literature on the subject, I""m not aware of any product capable of reproducing such a dynamic range, at least as far as the low or infra-low frequencies are concerned, which are the most difficult to reproduce in terms of power. This hoped for result is often unachievable due to environmental acoustics, which too often are not up to the reproduction system""standard, or at any rate don""t allow the original sound quality to be fully respected.
It must not be forgotten that for the sensitivity curve of the human ear, the difference between the loudness level at the center of the audible band (e.g. taking a value of 90 dBSPL and 1,000 Hz) and the level necessary for the same loudness at the bottom end of the audible band, 20 Hz is no less than 30 dB SPL.
Now since 30 dB (logarithmic measurement unit) are equivalent to 1,000 times in power, this means that when 1 Watt of power is applied to its terminals, a given loudspeaker is capable of reaching (for example) a level of 90 dBSPL at 1,000 Hz; to obtain the same loudness at 20 Hz, it""s necessary to use another loudspeaker with the same efficiency at the latter frequency as that of the former loudspeaker at 1,000 Hz, as well as a power capacity and mechanical construction able to support no less than 1,000 Watts applied to its terminals.
Although material and adhesive technology has now enabled the construction of loudspeakers with voice coils capable of supporting 1,000 electric Watts even for long periods without burning out, thanks also to ingenious cooling systems, this in fact occurs at relatively high frequencies, up to the transducer""s maximum effidency zone, usually at frequencies of between 100 and 200 Hz; however, this same technology definitely does not make this practice possible at gradually lower frequencies, even from 100 Hz: the entire loudspeaker is mechanically destroyed in a very short, regardless of the capacity of the voice coil to hold power without burning out.
This occurs because a loudspeaker""s diaphragm movement, necessary for the reproduction of low and infra-low frequencies at a high sound pressure levels, is almost always incompatible with its own intrinsic geometry or mechanical construction.
Moreover, even overlooking the fact that any loudspeaker which is capable of holding a sound signal applied to its input terminals with a power of 1,000 Watts would reproduce this signal with such a high distortion that no ear could bear i for a significant time, a larger quantity of loudspeakers, in a ratio of at least 1 to 10 or higher, according to the radiation conditions under which these units would have to operate, would have to be used to compensate for this enormous difference in efficiency, which is typical of woofers when reproducing low frequencies rather that those in the central band.
The premise is so generalized that it is possible to see with increasing regularity sound reinforcement systems using a section for the reproduction of low and infra-low frequencies composed of a large number (even ten) single high-power units linked together.
This is because of the need to obtain high sound levels which are distortion-free or almost when reproducing music, nowadays routine practice in all the types of related events; dubs, live concerts or even classical music reproduced live in stadiums for thousands of listeners, with the digital amplification of a large symphonic orchestra, or even modem films"" soundtracks which, thanks to digital recording, are able to recreate the sound""s level and quality in a captivatingly realistic manner.
All this obviously leads to a significant rise in costs and consumption due to the use of a large amount of electricity for powering numerous units together, as well as a rise in maintenance costs because of the greater possibility of repair work.
However, realistic high-level sound reproduction even for low and infra-low frequencies isn""t the only problem that prevents the intrinsic quality of modem sound production and/or recording techniques from being achieved.
In fact, rooms delegated mainly to the reproduction of music and speech (e.g. movie theaters, projection rooms, etc.) very often have architectural characteristics which considerably change the original sound played back inside them, even more so if levels must be kept high for the degree of realism required.
Walls that are parallel and often reflective, lack of homogeneous, well-distributed absorption for achieving optimal reverberation times for the venue and the type of program being reproduced lead to the concentration of greater energy on some frequency bands rather than others in certain positions in the room, according to the studies and statistics that have stood the test of time for decades.
In relatively small rooms, it""s even possible that so-called well-known stationary waves occur at low frequencies, greatly altering reproduction quality, masking medium and high frequency bands, whose intelligibility is indispensable to enable speech to be understood when there is an often extremely complex music program.
Generally speaking, rooms built in the past, but also nowadays, for the reproduction of the film soundtracks (e.g. movie theaters), often for budget reasons, have classical parallelepiped layouts with parallel walls, regardless of the fact that there are also the so-called xe2x80x9cbalconiesxe2x80x9d, even if these are less frequently built for cost reasons.
Moreover, apart from the necessary insulation towards the outside, internal acoustic treatment which should be very accurate to obtain the required reverberation curve according to the hall""s frequency and dimensions, is generally limited to the ceiling and (for reasons Intrinsic to the function) to the area of the floor on which the audience""s fabric-covered seating is installed.
Walls are rarely suitably well treated. xe2x80x9cFlutterxe2x80x9d echoes, xe2x80x9cslapxe2x80x9d echoes, unwanted reflections and stationary low-frequency waves often considerably worsen reproduction of soundtracks and speech in theaters screening films.
A first aim of the present invention is to overcome and solve the aforementioned problems regarding reproduction of low and infra-low frequencies, using an enclosure purposely designed and constructed for installation in rooms in which it""s often or always necessary to have a section available for the reproduction of low and infra-low frequencies able to give a sound level suited to the dimensions of the room in question and the events taking place in it.
A second aim of the invention is to solve the above-mentioned problems of the diffusion of sound in walled environments in a simple economic manner, particularly in the case of new or renovated buildings, based on the assumption that a particular design regarding a specific room is not necessary, but it""s sufficient to use modular architectural elements which are practical from an acoustic point of view and can be adapted from a structural point of view to any room, regardless of its specific pre-existent or new architecture.
These aims are achieved, according to the invention, using a sound diffusion system including, in combination or separately, at least one large cost-effective horn made of brickwork using traditional methods or prefabricated cement elements, assembled on-site in the foreseen position, and an architectural structure with a continuous or internittent xe2x80x9cmulti-henicylindricalxe2x80x9d surface covering the room""s walls, for the diffusion/reflection of the sound in wide spectrum of frequencies and at the same time for adjustable absorption of low and infra-low frequencies.
This large horn should preferably be located at the point in which the stage is installed in certain rooms, so that the upper covering of horn can be used as the stage surface, or at least the surface on which the stage is built.
The horn will be designed and built with parallel upper and lower walls, which will thus be load-bearing, able to support any weight on the top. The side walls will be curved (which can also be built using numerous straight sections) due to the need to comply with the necessary expansion of the horn area, provided for at the design stage and carefully calculated for the correct operation of this type of unit (i.e. the horn) as an acoustic load for a xe2x80x9cwooferxe2x80x9d loudspeaker, particularly if dedicated to accurate reproduction of low and infra-low frequencies.
The horn""s dimensions will be calculated, according to usable space, preferably (but not exclusively) to obtain, at the highest sound level possible from the loudspeakers or drivers, reproduction of low and ultra-low frequencies, starting at 200 Hz and going down to below or even under 20 Hz. This is the case when the sound being played back requires the reproduction of actual vibrations, perceptible to the body rather than the ear and necessary, for example, with the highly realistic recording of soundtracks involving natural phenomena, such as earthquakes, tidal waves, volcanoes or other explosions, often indispensable effects"" in recently produced films.
Even if the horn has the apparent drawback of not being able to be removed, due to the structural features described, in reality it offers absolutely the best solution to requirements connected with the reproduction of the low and infra-low frequencies, from the point of view of cost, performance and consumption.
Another structural detail not to be overlooked is the design of the system that drives the horn(s), in a section, which is separate from the horn and can be easily and securely fitted to it when required.
In other words, the loudspeaker or loudspeakers, which constitute the xe2x80x9cpowerhousexe2x80x9d of the system, will be housed in a dedicated xe2x80x9ccontainerxe2x80x9d with the volume required to produce the necessary rear load that these loudspeakers require for driving the horn correctly: this compact xe2x80x9ccontainerxe2x80x9d will be easily transported, thanks to its base""s built-in wheels.
As well as facilitating maintenance work, this solution solves any problem of system elements susceptible to damage being exposed to bad weather, vandalism or simply damage, in fact reducing, especially in the case of outdoor use, the decline in performance of the active elements (the loudspeakers), which will thus only be subject to wear due to their actual operation.
Another considerable advantage is due to the fact that travelling or touring shows, on which use is made of large amplification systems and therefore the appropriate number of cumbersome subwoofers, can use permanent local systems, with great savings from the point of view of transport (including that of the amplifiers) and energy consumed, while maintaining the reproduction quality of the low and infra-low frequency parts of the program.
Moreover, the horn system is directive in terms of width even at low frequencies, very advantageous for reducing undesired pollutant sound spill, unequalled by more expensive traditional systems, as they are necessarily constructed with dimensions suited to transport and therefore each individual unit is compact.
Moreover, from the point of view of performance, combining multiple units is only useful in the case of dimensions that are certainly much smaller than those in which the horn described can be constructed without any problem of interference.
In fact, whereas so many enclosures placed side by side to form a dimension greater than that of the wavelength of the frequency reproduced cause considerable harmful modifications in the polar response, due to interference and vibrations, although having large dimensions compared to the wavelengths of the band of frequencies reproduced, the horn according to the present invention behaves like one large source free from any interference or vibration capable of seriously deteriorating the program reproduced.
The architectural structure consists of a series of modules or panels having a hemicylindrical surface, which are equal or different in terms of chord and radius of curvature, constituting a xe2x80x9cmulti-hemicylindricalxe2x80x9d surface for covering the walls of a room, characterized by a lack of flat or concave surfaces. This may be run through by openings or holes with a width that can be modified or varied as required during construction.
This enables to obtain the desired diffusion of the entire spectrum of frequencies required in a foreseeable manner, because it is closely related to the dimension of the xe2x80x9chemicylindricalxe2x80x9d elements and the distance between them and between them and the wall, according to procedures that are well known in acoustics, and at the same time to obtain low frequency acoustic absorption which is adjustable, thanks to the possibility of dosing the holes or openings in the said xe2x80x9chemicylindricalxe2x80x9d elements successively and empirically, after their installation in the room.
The results of using these architectural elements lies in the advantageous contribution of the room to the reproduction of wide-band sound with even spatial distribution throughout the entire xe2x80x9caudiencexe2x80x9d which has (without appreciable differences in level or quality between zones) greater presence and thus maximum sound spectacularity, without the typical limitations of traditional rooms.
The attached drawings illustrate in a non-limiting manner some possible embodiments of the present invention of a horn-type diffuser designed for a rapid connection of the active driver part to its throat and having an architectural structure for the covering of walls.